All-Nanosheet Ultrathin Capacitors Assembled Layer-by-Layer via Solution-Based Processes

Abstract

All-nanosheet ultrathin capacitors of Ru0.95O20.2-/Ca2Nb3O10-/Ru0.95O20.2- were successfully assembled through facile room-temperature solution-based processes. As a bottom electrode, conductive Ru0.95O20.2- nanosheets were first assembled on a quartz glass substrate through a sequential adsorption process with polycations. On top of the Ru0.95O20.2- nanosheet film, Ca2Nb3O10- nanosheets were deposited by the Langmuir-Blodgett technique to serve as a dielectric layer. Deposition parameters were optimized for each process to construct a densely packed multilayer structure. The multilayer buildup process was monitored by various characterizations such as atomic force microscopy (AFM), ultraviolet-visible absorption spectra, and X-ray diffraction data, which provided compelling evidence for regular growth of Ru0.95O20.2- and Ca2Nb3O10- nanosheet films with the designed multilayer structures. Finally, an array of circular films (50 μm ϕ) of Ru0.95O20.2- nanosheets was fabricated as top electrodes on the as-deposited nanosheet films by combining the standard photolithography and sequential adsorption processes. Microscopic observations by AFM and cross-sectional transmission electron microscopy, as well as nanoscopic elemental analysis, visualized the sandwich metal-insulator-metal structure of Ru0.95O20.2-/Ca2Nb3O10-/Ru0.95O20.2- with a total thickness less than 30 nm. Electrical measurements indicate that the system really works as an ultrathin capacitor, achieving a capacitance density of ∼27.5 μF cm(-2), which is far superior to currently available commercial capacitor devices. This work demonstrates the great potential of functional oxide nanosheets as components for nanoelectronics, thus contributing to the development of next-generation high-performance electronic devices.

Vertical 2D Heterostructures

“…Electrochemical capacitors are promising candidates for energy storage devices owing to their high specific power and long cycle life, and efforts are being made to develop in-plane or ultrathin all-solid-state supercapacitors (97), which are intriguing energy storage components for flexible/stretchable and portable electronic devices with high safety requirements. To improve the specific capacitance of carbonaceous electrochemical double-layer capacitors that store energy by means of reversible electroadsorption of ions in the Helmholtz double layer at the electrode/electrolyte interface, graphene-based supercaps have been hybridized with pseudocapacitive nanosheets, including transition metal oxides, hydroxides, and chalcogenides.…”

Understanding the structural, electrical, and optical properties of monolayer h-phase RuO2 nanosheets: a combined experimental and computational study

“…In recent years, RuO 2 NSs exfoliated from bulk rutile RuO 2 have been used in lithium-oxygen and lithium-ion battery applications because exfoliation facilitates the fabrication of NSs 15,16 . Wang et al 17 reported obtaining a sheet resistance of 4.1 kΩ sq −1 from RuO 2 NS films at room temperature, although most of their work focused on all NS ultrathin capacitors. Recently, Lee et al 18 also demonstrated the optimization Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 16678, Republic of Korea Full list of author information is available at the end of the article of electrode performance using exfoliated 2D RuO 2 NSs as a conducting additive.…”

Preparation and electrode properties of novel redoxable nanosheets of Mn–Ni oxide with and without vacancy defects

“…11),15), 16) Because MnO 2 nanosheets are redoxable, they are expected to be suitable for energy storage devices or solar cells, and their electrode properties for use lithium-ion batteries have been examined. 17) Lithium-ion rechargeable batteries have the advantage of higher energy density than other types of commercial batteries, therefore they are used as energy-storage instruments in various mobile electric devices.…”

“…RuO 2.1 nanosheets (or Ru 0.95 O 2 nanosheets) should also have the Ru-site vacancy of this type. 6), 16) While in the other study the concentration of the vacancy defects is fixed, the process employed here has the potential to control the concentration of the vacancy defects by changing the composition of the starting material or the condition of acid-restacking.…”